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Mole salamanders | |
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Spotted salamander (Ambystoma maculatum) | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Amphibia |
Order: | Urodela |
Family: | Ambystomatidae |
Genus: | Ambystoma Tschudi, 1838 |
The mole salamanders (genus Ambystoma) are a group of advanced salamanders endemic to North America. The group has become famous due to the presence of the axolotl (A. mexicanum), widely used in research due to its paedomorphosis, and the tiger salamander (A. tigrinum, A. mavortium) which is the official amphibian of many US states, and often sold as a pet.
Terrestrial mole salamanders are identified by having wide, protruding eyes, prominent costal grooves, and thick arms. Most have vivid patterning on dark backgrounds, with marks ranging from deep blue spots to large yellow bars depending on the species. Terrestrial adults spend most of their lives underground in burrows, either of their own making or abandoned by other animals. Some northern species may hibernate in these burrows throughout the winter. They live alone and feed on any available invertebrate. Adults spend little time in the water, only returning to the ponds of their birth to breed.
All mole salamanders are oviparous and lay large eggs in clumps in the water. Their fully aquatic larvae are branchiate, with three pairs of external gills behind their heads and above their gill slits. Larvae have large caudal fins, which extend from the back of their heads to their tails and to their cloacae. Larvae grow limbs soon after hatching, with four toes on the fore arms, and five toes on the hind legs. Their eyes are wide-set and lack true eyelids.
The larvae of some species (especially those in the south, and tiger salamanders) can reach their adult size before undergoing metamorphosis. During metamorphosis, the gills of the larvae disappear, as do the fins. Their tails, skin, and limbs become thicker, and the eyes develop lids. Their lungs become fully developed, allowing for a fully terrestrial existence.
Some species of mole salamanders (as well as populations of normally terrestrial species) are neotenic (retaining their larval form into adulthood). The most famous example is the axolotl. They cannot produce thyroxine, so their only means of metamorphosis is mainly through the outside injection of it. This usually shortens the lifespan of the salamander.
The presence of neotenic populations near those with large larvae has made it difficult to identify mole salamander species. The tiger salamander complex was previously considered a single species ranging from Canada to Mexico, falling under the name A. tigrinum. Despite differences in coloration and larvae, tiger salamanders were found throughout their unbroken range, which made it difficult to delineate subspecies, let alone elevate any populations to species status. In morphological terms, tiger salamanders are all very similar, with large heads, small eyes, and thick bodies. This is probably because tiger salamanders have the primitive morphology of mole salamanders. They are also the largest of the mole salamanders, and have very large larvae. All populations have similar lifestyles, and their lifecycles are identical. However, when one looks at tiger salamander populations distant from each other, different species within this complex become apparent. The ranges of these potential species overlap, and hybridization occurs, blurring the lines between species.
Several subspecies of A. tigrinum were named to deal with this problem. Recently, the barred tiger salamander (A. mavortium) was elevated to species status—covering the tiger salamander populations in the western and central United States. Several distinct subspecies still exist in A. mavortium, which may be elevated to species status at some point in the future. The California tiger salamander (A. californiense) has also been elevated out of A. tigrinum, and is actually very distantly related to all other mole salamander species. The Plateau tiger salamander (A. velasci) was elevated out of A. tigrinum through genetic analysis in 1997. All accounts referring to the axolotl (A. mexicanum) as a close relative of A. tigrinum are now considered wrong, as they are now separated by both geography and many species between. Instead, it is A. velasci, which shares the axolotl's habitat, and is probably closely related to it. The Plateau tiger salamander was probably the parent of most of the neotenic species, which raises the possibility that A. velasci is paraphyletic, and may be broken up into more species in the future.
![]() | It has been suggested that this article should be split into a new article titled Unisexual salamander . (discuss) (April 2024) |
Unisexual (all-female) populations of ambystomatid salamanders are widely distributed across the Great Lakes region and northeastern North America. The females require sperm from a co‑occurring, related species to fertilize their eggs and initiate development. Usually [1] the eggs then discard the sperm genome and develop asexually (i.e., gynogenesis, with premeiotic doubling); however, they may incorporate the genome from the sperm into the resulting offspring. [2] Sperm incorporation commonly [1] takes the form of genome addition (resulting in ploidy elevation in the offspring), or genome replacement, wherein one of the maternal genomes is discarded. This unique mode of reproduction has been termed kleptogenesis by Bogart and colleagues. [2] This is in contrast to hybridogenesis, where the maternal genomes are passed hemiclonally and the paternal genome is discarded every generation before the egg matures and reacquired from the sperm of another species.
The nuclear DNA of the unisexuals generally comprises genomes from up to five species: [3] the blue-spotted salamander (A. laterale), Jefferson salamander (A. jeffersonianum), small-mouthed salamander (A. texanum), streamside salamander (A. barbouri), and tiger salamander (A. tigrinum), denoted respectively as L, J, Tx, B, and Ti. This flexibility results in a large number of possible nuclear biotypes (genome combinations) in the unisexuals. For example, an LJJ individual would be a triploid with one A. laterale genome and two A. jeffersonianum genomes, while an LTxJTi individual would be a tetraploid with genomes from four species. Because they have hybrid genomes, unisexual salamanders are a cryptic species with morphology similar to coexisting species. For example, LLJs look like blue-spotted salamanders and LJJs look like Jefferson salamanders. Silvery salamanders LJJ (A. platineum), Tremblay's salamanders LLJ (A. tremblayi), and Kelly's Island salamanders LTxTx and LTxTi (A. nothagenes) were initially described as species. Species names were later dropped for all unisexual salamanders because of the complexity of their genomes. The offspring of a single mother may have different genome complements; [2] for example, a single egg mass may have both LLJJ and LJJ larvae.
Despite the complexity of the nuclear genome, all unisexuals form a monophyletic group based on their mitochondrial DNA. The maternal ancestor of the unisexual ambystomatids was most closely related to the streamside salamander, with the original hybridization likely occurring 2.4~3.9 million years ago, [2] making it the oldest known lineage of all-female vertebrates. [4] The hybridization was most probably with an A. laterale. All known unisexuals have at least one A. laterale genome [3] and this is thought to be essential for unisexuality. However, the A. laterale genome has been replaced several times, independently, in each of the lineages by matings with A. laterale.
Ambystoma mexicanum, a neotenic salamander with exceptional regenerative capabilities is one of the principal models for studying limb regeneration. [5] Limb regeneration involves the propagation of a mass of low differentiated and highly proliferative cells termed the blastema. [5] [6] During limb regeneration, blastema cells experience DNA double-strand breaks and thus require homologous recombination, a form of DNA repair that deals with double-strand breaks. [6]
Rhyacosiredon was previously considered a separate genus within the family Ambystomatidae. However, cladistic analysis of the mole salamanders found the existence of Rhyacosiredon makes Ambystoma paraphyletic, since the species are more closely related to some Ambystoma species than those species are to others in Ambystoma. The stream-type morphology of these salamanders (which includes larvae and neotenes with short gills and thicker gular folds) may have led to their misclassification as a different genus.
The genus name Ambystoma was given by Johann Jakob von Tschudi in 1839, [7] and is traditionally translated as "cup-mouth",[ citation needed ]. Tschudi did not provide a derivation for the name, and many thought that he intended the name Amblystoma, "blunt-mouth." Occasionally, old specimens and documents use the name Amblystoma. Writing in 1907, Leonhard Stejneger offered a derivation of Ambystoma based on the contraction of a Greek phrase meaning "to cram into the mouth," [8] [9] but others have not found this explanation convincing. [10] In the absence of clear evidence that Tschudi committed a lapsus, the name given in 1839 stands.
This genus contains 32 species, listed below, the newest being A. bishopi. Some Ambystoma species are Terrestrial, others are neotenic, and some species have established populations of both neotenic and terrestrial forms.
Image | Species and author | Common name | Distribution | Lifestyle | IUCN status |
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![]() | A. altamirani Dugès, 1895 | Mountain stream salamander, Achoque | Central Mexico, west and south of the Valley of Mexico | Terrestrial and neotenic | ![]() |
A. amblycephalum Taylor, 1940 | Blunt-headed salamander | West-central Mexico (Michoacán state), near Morelia | Terrestrial and neotenic | ![]() | |
![]() | A. andersoni | Anderson's salamander | West-central Mexico (Michoacán state), Laguna de Zacapu | Neotenic | ![]() |
![]() | A. annulatum Cope, 1886 | Ringed salamander | South-central United States (Arkansas, Illinois, Missouri, Oklahoma), Ozark Plateau and Ouachita Mountains | Terrestrial | ![]() |
![]() | A. barbouri Kraus & Petranka, 1989 | Streamside salamander | South-midwest United States (Indiana, Kentucky, Ohio, Tennessee, West Virginia) | Terrestrial | ![]() |
A. bishopi | Reticulated flatwoods salamander | Southeast United States (Florida Panhandle and southernmost Georgia), west of the Apalachicola-Flint River | Terrestrial | ![]() | |
A. bombypellum (Taylor, 1940) | Delicate-skinned salamander | Central Mexico (State of Mexico) near Jilotepec | Terrestrial | ![]() | |
![]() | A. californiense Gray, 1853 | California tiger salamander | Central Valley of California | Terrestrial | ![]() |
![]() | A. cingulatum Cope, 1868 | Frosted flatwoods salamander | Southeast United States (southern South Carolina and Georgia south to northern Florida) | Terrestrial | ![]() |
![]() | A. dumerilii (Dugès, 1870) | Lake Pátzcuaro salamander, Achoque | West-central Mexico (Michoacán state), Lake Pátzcuaro | Neotenic | ![]() |
![]() | A. flavipiperatum Dixon, 1963 | Yellow-peppered salamander, Ajolote de Chapala | West-central Mexico (Jalisco) | Terrestrial | ![]() |
![]() | A. gracile (Baird, 1859) | Northwestern salamander | Northwest North America (southernmost Alaska to northern California) | Terrestrial | ![]() |
A. granulosum Taylor, 1944 | Granular salamander, Ajolote | Central Mexico (State of Mexico) near Toluca | Terrestrial | ![]() | |
![]() | A. jeffersonianum (Green, 1827) | Jefferson salamander | Northeastern North America (Ontario south to Virginia and west to Illinois) | Terrestrial | ![]() |
![]() | A. laterale Hallowell, 1856 | Blue-spotted salamander | Northeastern North America (Nova Scotia west to Manitoba and Minnesota and south to Indiana and New Jersey) | Terrestrial | ![]() |
![]() | A. leorae Taylor, 1943 | Leora's stream salamander, Ajolote | Central Mexico (Mexico state - Puebla border), Mount Tlaloc | Terrestrial | ![]() |
A. lermaense (Taylor, 1940) | Lake Lerma salamander | Central Mexico (State of Mexico), Lake Lerma near Toluca | Terrestrial and neotenic | ![]() | |
![]() | A. mabeei Bishop, 1928 | Mabee's salamander | Coastal southeast United States (southeast Virginia to South Carolina) | Terrestrial | ![]() |
![]() | A. macrodactylum Baird, 1950 | Long-toed salamander | Northwest North America (Alaska south to northern California and east to Alberta and Montana) | Terrestrial | ![]() |
![]() | A. maculatum (Shaw, 1802) | Spotted salamander | Eastern North America (Nova Scotia west to Wisconsin and south to eastern Texas and Georgia) | Terrestrial | ![]() |
![]() | A. mavortium Baird, 1850 | Barred tiger salamander | Western North America (Manitoba south to Texas and west to Washington and California) | Terrestrial and neotenic | ![]() |
| A. mexicanum | Axolotl | Central Mexico (State of Mexico), Lake Xochimilco | Neotenic | ![]() |
![]() | A. opacum (Gravenhorst, 1807) | Marbled salamander | Eastern United States (New Hampshire south to northern Florida and east to Missouri and Texas) | Terrestrial | ![]() |
A. ordinarium Taylor, 1940 | Puerto Hondo stream salamander | West-central Mexico (Michoacán state), Puerto Hondo stream | Terrestrial and neotenic | ![]() | |
![]() | A. rivulare Taylor, 1940 | Michoacan stream salamander | Central Mexico (western State of Mexico) | Terrestrial and neotenic | ![]() |
![]() | A. rosaceum Taylor, 1941 | Tarahumara salamander | Northwest Mexico, Sierra Madre Occidental | Terrestrial and neotenic | ![]() |
A. silvense Webb, 2004 | Durango salamander | Northwest Mexico (Durango and Chihuahua), Sierra Madre Occidental | Terrestrial and neotenic | ![]() | |
![]() | A. talpoideum Holbrook, 1838 | Mole salamander | Southeast United States (Virginia west to Oklahoma and south to northern Florida) | Terrestrial and neotenic | ![]() |
![]() | A. taylori Brandon, Maruska, and Rumph, 1982 | Taylor's salamander | Southeast Mexico (Puebla), Laguna Alchichica | Neotenic | ![]() |
![]() | A. texanum Matthes, 1855 | Small-mouth salamander | South-central United States (Ohio west to Nebraska and south to Texas and Alabama) | Terrestrial | ![]() |
![]() | A. tigrinum (Green, 1825) | Eastern tiger salamander | Eastern North America (New York northwest to Manitoba and south to Texas and northern Florida) | Terrestrial and neotenic | ![]() |
![]() | A. velasci (Dugès, 1888) | Plateau tiger salamander | Mexican Plateau | Terrestrial and neotenic | ![]() |
In addition, two groups of unisexual hybrid populations are sometimes named under their own species:
Neoteny, also called juvenilization, is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared to other primates. In progenesis or paedogenesis, sexual development is accelerated.
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata. Urodela is a scientific Latin term based on the Ancient Greek οὐρά δήλη: ourà dēlē "conspicuous tail". Caudata is the Latin for "tailed ones", from cauda : "tail".
The axolotl is a paedomorphic salamander closely related to the tiger salamander. It is unusual among amphibians in that it reaches adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco. These lakes were drained by Spanish settlers after the conquest of the Aztec Empire, leading to the destruction of much of the axolotl's natural habitat.
The tiger salamander is a species of mole salamander and one of the largest terrestrial salamanders in North America.
Ambystomatidae is a family of salamanders belonging to the Suborder Salamandroidea in the class Amphibia. It contains two genera, Ambystoma and Dicamptodon. Ambystoma contains 32 species and are distributed widely across North America, while Dicamptodon contains four species restricted to the Pacific Northwest. These salamanders are mostly terrestrial and eat invertebrates, although some species are known to eat smaller salamanders. They can be found throughout the US and some areas of Canada in damp forests or plains. This family contains some of the largest terrestrial salamanders in the world, the tiger salamander and the coastal giant salamander. Some species are toxic and can secrete poison from their bodies as protection against predators or infraspecific competition. Neoteny has been observed in several species in Ambystomatidae, and some of them like the axolotl live all of their lives under water in their larval stage.
The blue-spotted salamander is a mole salamander native to the Great Lakes states and northeastern United States, and parts of Ontario and Quebec in Canada. Their range is known to extend to James Bay to the north, and southeastern Manitoba to the west.
A blastema is a mass of cells capable of growth and regeneration into organs or body parts. The changing definition of the word "blastema" has been reviewed by Holland (2021). A broad survey of how blastema has been used over time brings to light a somewhat involved history. The word entered the biomedical vocabulary in 1799 to designate a sinister acellular slime that was the starting point for the growth of cancers, themselves, at the time, thought to be acellular, as reviewed by Hajdu. Then, during the early nineteenth century, the definition broadened to include growth zones in healthy, normally developing plant and animal embryos. Contemporaneously, cancer specialists dropped the term from their vocabulary, perhaps because they felt a term connoting a state of health and normalcy was not appropriate for describing a pathological condition. During the middle decades of the nineteenth century, Schleiden and Schwann proposed the cell theory, and Remak and Virchow insisted that cells can only be generated by division of existing ones. Consequently, the conception of the blastema changed from acellular to cellular. More specifically, the term came to designate a population of embryonic cells that gave rise to a particular tissue. In short, the term blastema started being used to refer to what modern embryologists increasingly began calling a rudiment or Anlage. Importantly, the term blastema did not yet refer to a mass of undifferentiated-looking cells that accumulates relatively early in a regenerating body part. For instance, Morgan (1900), does not use the term even once in his classic book, “Regeneration.” It was not until the eve of World War 1 that Fritsch introduced the term blastema in the modern sense, as now used by contemporary students of regeneration. Currently, the old usage of blastema to refer to a normal embryological rudiment has largely disappeared.
The ringed salamander is a species of mole salamander native to hardwood and mixed hardwood-pine forested areas in and around the Ozark Plateau and Ouachita Mountains of Arkansas, Oklahoma, and Missouri. This species of salamander has slander body, small head, and long tail. They are usually found to have various dorsal color from dark gray to dark brown. Various close relatives are found such as marbled salamander and spotted salamander. This species of salamander has cannibal behavior especially those in large body size.
The long-toed salamander is a mole salamander in the family Ambystomatidae. This species, typically 4.1–8.9 cm (1.6–3.5 in) long when mature, is characterized by its mottled black, brown, and yellow pigmentation, and its long outer fourth toe on the hind limbs. Analysis of fossil records, genetics, and biogeography suggest A. macrodactylum and A. laterale are descended from a common ancestor that gained access to the western Cordillera with the loss of the mid-continental seaway toward the Paleocene.
The Lake Patzcuaro salamander, locally known as achoque, is a paedomorphic species of salamander found exclusively in Lake Pátzcuaro, a high-altitude lake in the Mexican state of Michoacán. First described in 1870 by Alfredo Dugès, the species is named in honor of the French herpetologist Auguste Duméril. However, the salamander has been used as a food source and an ingredient in traditional medicines by the Purépecha people since the Pre-Columbian era. Ambystoma dumerilii are neotenic, meaning they retain their larval characteristics throughout their entire life. This results in adults that have long, heavily filamented external gills, gill slits lined with tooth-like gill rakers, and caudal fins. When stressed, Ambystoma dumerilii can undergo an incomplete metamorphosis, though this is process significantly decreases their lifespan and is often fatal.
The Puerto Hondo stream salamander or Michoacan stream salamander is a mole salamander from the Trans-Mexican Volcanic Belt within the Mexican state of Michoacán.
Ambystoma talpoideum, the mole salamander, is a species of salamander found in much of the eastern and central United States, from Florida to Texas, north to Illinois, east to Kentucky, with isolated populations in Virginia and Indiana. Older sources often refer to this species as the tadpole salamander because some individuals remain in a neotenic state. This salamander lives among the leaf litter on the forest floor, migrating to ponds to breed.
The barred tiger salamander or western tiger salamander is a species of mole salamander that lives in lower western Canada, the western United States and northern Mexico.
The plateau tiger salamander or Mexican tiger salamander is a species of mole salamander in the family Ambystomatidae. It is typically considered endemic to Mexico, although its range might extend to the United States. Its natural habitat is grassland, including sparse forest and semiarid grassland. Breeding takes place in a range of aquatic habitats: deep volcanic lakes, shallow vernal pools, artificial cattle ponds, and intermittent, fish-free stream pools. It exhibits facultative paedomorphosis.
The silvery salamander is a hybrid species of mole salamander from the United States of America and Canada. It is usually between 5.5–7.75 in (14.0–19.7 cm) long and is slender with many small silvery-blue spots on its back and sides. It is brownish grey and the area around its vent is grey. A unisexual Ambystoma hybrid species, Ambystoma platineum has been grouped with other unisexual ambystomatids that takes genetic material from Jefferson salamanders, streamside salamanders, small-mouthed salamanders, tiger salamanders and the blue-spotted salamander.
In biology, a klepton and synklepton is a species that requires input from another biological taxon to complete its reproductive cycle. Specific types of kleptons are zygokleptons, which reproduce by zygogenesis; gynokleptons which reproduce by gynogenesis, and tychokleptons, which reproduce by a combination of both systems.
Parthenogenesis is a form of reproduction where eggs develop without fertilization, resulting in unisexual species. This phenomenon is closely related with reproductive modes such as hybridogenesis, where fertilization occurs, but the paternal DNA is not passed on. Among amphibians, it is seen in numerous frog and salamander species, but has not been recorded in caecilians.
Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.
Data related to Ambystomatidae at Wikispecies
Media related to Ambystoma at Wikimedia Commons